1. Field of the Invention
The present invention relates to a regulating unit and a radiographic imaging system. More particularly, the present invention relates to a regulating unit and a radiographic imaging system, in which a radiographic imaging unit has a function of automatic exposure control (AEC), and safety in the function can be maintained even in use of plural AEC signal output devices.
2. Description Related to the Prior Art
An X-ray imaging system as a radiographic imaging system is well-known in the field of medical imaging. The X-ray imaging system includes an X-ray generating apparatus as a radiation generating apparatus, and an X-ray imaging apparatus as a radiographic imaging apparatus. The X-ray imaging apparatus forms an X-ray image from X-rays transmitted through a body of a patient. The X-ray generating apparatus includes an X-ray source as a radiation source, a radiation source driver and a source switch. The X-ray source applies X-rays to an object. The radiation source driver controls the X-ray source. The source switch is operable to input a command signal for starting the irradiation to the radiation source driver. The X-ray imaging apparatus includes an electronic cassette or a radiographic imaging unit, and a computer terminal or console unit. The radiographic imaging unit detects the X-ray image from X-rays transmitted through the body having various body parts. The computer terminal drives and controls the radiographic imaging unit, and stores and displays the X-ray image.
An FPD device (flat panel detector device) has been recently utilized as the radiographic imaging panel as a newly developed device in place of an X-ray film or imaging plate (IP). The FPD device has an imaging area in which arrays of pixels are arranged for storing signal charge according to dose of incident X-rays. The FPD device stores signal charge per pixels, reads the stored signal charge through switching elements such as TFTs, and electrically detects the X-ray image by conversion of the signal charge into voltage signal in a signal processor.
Various medical service providers have wishes to use the radiographic imaging unit in combination with an X-ray film or imaging plate conventionally used widely even after introducing the radiographic imaging unit with the FPD device. A new type of the X-ray generating apparatus is marketed for compatibility with the radiographic imaging unit having the FPD device and the X-ray film or imaging plate. Also, an improvement of and an additional structure to the X-ray generating apparatus for the X-ray film or imaging plate have been suggested so that the X-ray generating apparatus for the X-ray film or imaging plate can become compatible with the radiographic imaging unit having the FPD device. The additional structure is disclosed in U.S. Pat. Nos. 7,844,031 and 8,085,901 (corresponding to JP-A 2011-502699).
In the FPD device, the resetting is periodically carried out for the purpose of removing charge from the pixels to minimize influence of electric noise of dark current in the X-ray image, as a difference from the X-ray film or imaging plate. It is necessary to synchronize a start of the storing after the resetting with a start of irradiation of X-rays from the X-ray source. U.S. Pat. Nos. 7,844,031 and 8,085,901 disclose a relay device (for connection and control) for connection of the source switch (operable switch), the radiation source driver (computer and the X-ray source), and the radiographic imaging unit (DR receiver panel) having the FPD device. The relay device sends a start signal or exposure signal to both of the radiation source driver and the radiographic imaging unit for synchronism. Thus, the radiographic imaging unit having the FPD device can be used with the X-ray generating apparatus for the X-ray film or imaging plate.
Also, U.S. Pat. Nos. 7,844,031 and 8,085,901 disclose a use of an external AEC signal output device (detection device), which is separate from the radiographic imaging unit, and shuts off irradiation of X-rays from the X-ray source when it is judged that the cumulative dose of the X-rays reaches a target dose. The external AEC signal output device is connected to the radiation source driver, and generates an AEC signal as a result of a detected dose of X-rays, or occurrence of the reach of the cumulative dose to the target dose. The radiation source driver shuts off the irradiation in response to the AEC signal.
There is a type of the radiographic imaging unit with the FPD device in which a built-in AEC signal output device (detection device) is incorporated. It is conceivable to combine the use of the built-in AEC signal output device with the use of the external AEC signal output device separate from the radiographic imaging unit as suggested in U.S. Pat. Nos. 7,844,031 and 8,085,901. However, there occurs a crosstalk between the AEC signals from the external AEC signal output device and the built-in AEC signal output device in the case of their simultaneous use. No AEC is carried out properly due to failure in operation of the radiation source driver, to expose an object to X-rays of a harmfully high dose.
U.S. Pat. Nos. 7,844,031 and 8,085,901 disclose synchronism between a start of the storing of the FPD device and a start of irradiation. However, no built-in AEC signal output device is included in the radiographic imaging unit with the FPD device. No solution is known for the problem with the combined use of the built-in AEC signal output device in the radiographic imaging unit with the FPD device and the external AEC signal output device separate from the radiographic imaging unit.